The Celtic Channel, as I call it, is better known as the Irish or North Channel. It is the body of water separating the two very proud Celtic nations of Irish and the Scots. The straight line distance from Donaghadee to Poartpatrick is 34k. Most swimmers go much further than this. It is widely regarded as the most difficult of the Oceans 7 swims. Being further north than the more well known English Channel, the water is colder (12-14 degs C) with strong currents and, of course, the infamous Lions Mane jellyfish. The weather patterns are less predictable than the English Channel, which can lead to less swimmable days during a neap tide.